Edge-lit lighting device

ABSTRACT

A circular edge-lit lighting device includes a light emitting panel (LEP) and a first light emitting diode (LED) light source positioned proximal to a first location on a narrow outer perimeter edge of the LEP. The first LED light source is configured to emit a first light into the LEP through the narrow outer perimeter edge. The first light has a first intensity level. The circular edge-lit lighting device also includes a second LED light source positioned proximal to a second location on the narrow outer perimeter edge the LEP. The second LED light source is configured to emit a second light into the LEP through the narrow outer perimeter edge. The second light has a second intensity level. The first location and the second location are different locations.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claims priority to U.S.Nonprovisional patent application Ser. No. 15/186,122, filed Jun. 17,2016, and titled “Edge-Lit Lighting Device,” which claims priority toU.S. Nonprovisional patent application Ser. No. 14/011,446, filed Aug.27, 2013, and titled “Light Distribution Control of an Edge-Lit LightingDevice,” the entire contents of the foregoing applications are herebyincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to light distribution control,in particular to light distribution control of an edge-lit lightingdevice.

BACKGROUND

Edge-lit lighting fixtures include a light emitting panel (LEP) thatemits light through a broad side of the LEP. For example, the lightingfixture may include a light source, such as a light emitting diode(LED),that is positioned close to one of the multiple narrow sides ofthe LEP. Light from the light source may enter the LEP through a narrowside of the LEP. The light from the light source that enters the LEPthrough the narrow side of the LEP may be emitted by the LEP through thebroad side of the LEP to illuminate a space around the lighting fixture.Distribution pattern of the light emitted by the LEP of the lightingfixture may depend on, for example, the intensity of the light that isemitted by the light source and that enters the narrow side of the LEP.The distribution pattern of the light emitted by the LEP may also dependon the particular narrow side of multiple narrow sides of the LEPthrough which the light from the light source enters the LEP.

In some cases, the distribution pattern of light emitted by a standardedge-lit lighting fixture may not be desirable for some applicationsand/or situations. For example, an edge-lit lighting fixture that emitslight that equally illuminates all parts of area around the lightingfixture may not be desirable. To illustrate, a series of lightingfixtures may be powered to provide lighting for a parking (deck) garage.However, it may be undesirable for the light to illuminate areas outsideof the parking garage. To avoid illuminating some areas around thelighting fixtures, the lighting fixtures may need to include structuressuch as inserts and/or shields. Furthermore, not only illumination ofsome areas around the lighting fixture may be undesirable, the need forillumination of an area around the lighting fixture may change based onparticular situations. For example, an area around the lighting fixturemay need to be illuminated only when the area is occupied.

Accordingly, a lighting device that can be set and/or adjusted to emitlight that has a particular distribution pattern may be desirable.

SUMMARY

In general, the present disclosure relates to light distribution controlof an edge-lit lighting device. In an example embodiment, an edge-litlighting device includes a light emitting panel (LEP), a first pluralityof light sources, and a second plurality of LEDs. The first plurality oflight sources are positioned proximal to a first narrow side of the LEPand are configured to emit a first light into the LEP through the firstnarrow side. The first light has a first intensity level. The secondplurality of LEDs are positioned proximal to a second narrow side of theLEP and are configured to emit a second light into the LEP through thesecond narrow side. The second light has a second intensity level thatis different from the first intensity level. The first intensity leveland the second intensity level are set to achieve a particulardistribution pattern of an output light emitted out through a broad sideof the LEP.

In another example embodiment, an edge-lit lighting device includes alight emitting panel (LEP), a first plurality of light sources, and asecond plurality of light sources. The first plurality of LEDs arepositioned proximal to a first narrow side of the LEP and are configuredto emit a first light into the LEP through the first narrow side. Thefirst light has a first intensity level. The second plurality of LEDsare positioned proximal to a second narrow side of the LEP and areconfigured to emit a second light into the LEP through the second narrowside. The second light has a second intensity level. The LEP isconfigured to emit out an output light through a broad side of the LEP.The first intensity level and the second intensity level of the secondlight are adjustable. The distribution pattern of the output light ischangeable by adjusting one of the first intensity level and the secondintensity level.

In another example embodiment, a method of controlling lightdistribution of an edge-lit lighting device includes installing anedge-lit lighting device that includes a light emitting panel (LEP), afirst plurality of light sources positioned proximal to a first narrowside of the LEP and configured to emit a first light into the LEPthrough the first narrow side, and a second plurality of light sourcespositioned proximal to a second narrow side of the LEP and configured toemit a second light into the LEP through the second narrow side. Themethod further includes setting an intensity level of the first light,and setting an intensity level of the second light.

In another example embodiment, an edge-lit lighting device includes alight emitting panel (LEP) having a broad side and a plurality narrowsides. The edge-lit lighting device further includes multiple lightsources. Each of the multiple light sources is positioned proximal to arespective narrow side of the plurality of narrow sides and oriented toemit a respective light into the LEP through the respective narrow sideof the plurality of narrow sides. A distribution of an output lightemitted out through the broad side of the LEP is changeable by poweringon at least one light source of the multiple light sources that arepowered off and by powering off one or more light sources of themultiple light sources that are powered on.

These and other aspects, objects, features, and embodiments will beapparent from the following description and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying figures, which are notnecessarily to scale, and wherein:

FIGS. 1A and 1B illustrates a lighting device including a light emittingpanel (LEP) in accordance with an example embodiment;

FIG. 2A illustrates the lighting device of FIG. 1A including a set oflight emitting diodes (LEDs) that are powered on in accordance with anexample embodiment;

FIG. 2B illustrates an Iso-footcandle plot that corresponds to thelighting device of FIG. 2A in accordance with an example embodiment;

FIG. 3A illustrates the lighting device of FIG. 1A including two sets ofLEDs that are powered on in accordance with an example embodiment;

FIG. 3B illustrates an Iso-footcandle plot that corresponds to thelighting device of FIG. 3A in accordance with an example embodiment;

FIG. 4A illustrates the lighting device of FIG. 1A including two sets ofLEDs that are powered on in accordance with another example embodiment;

FIG. 4B illustrates an Iso-footcandle plot that corresponds to thelighting device of FIG. 4A in accordance with an example embodiment;

FIG. 5A illustrates the lighting device of FIG. 1A including three setsof LEDs that are powered on in accordance with an example embodiment;

FIG. 5B illustrates an Iso-footcandle plot that corresponds to thelighting device of FIG. 5A in accordance with an example embodiment;

FIG. 6A illustrates the lighting device of FIG. 1A including four setsof LEDs that are powered on in accordance with an example embodiment;

FIG. 6B illustrates an Iso-footcandle plot that corresponds to thelighting device of FIG. 6A in accordance with an example embodiment;

FIGS. 7A-7D are Iso-footcandle plots illustrating effects of differentintensity levels of light from different light sources on the lightdistribution pattern of a lighting device in accordance with an exampleembodiment; and

FIG. 8 is a flowchart illustrating a method of controlling lightdistribution of the edge-lit lighting device of FIG. 1A in accordancewith an example embodiment.

The drawings illustrate only example embodiments and are therefore notto be considered limiting in scope. The elements and features shown inthe drawings are not necessarily to scale, emphasis instead being placedupon clearly illustrating the principles of the example embodiments.Additionally, certain dimensions or placements may be exaggerated tohelp visually convey such principles. In the figures, reference numeralsdesignate like or corresponding, but not necessarily identical,elements.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

In the following paragraphs, particular embodiments will be described infurther detail by way of example with reference to the figures. In thedescription, well known components, methods, and/or processingtechniques are omitted or briefly described. Furthermore, reference tovarious feature(s) of the embodiments is not to suggest that allembodiments must include the referenced feature(s).

Turning now to the drawings, example embodiments are described. FIGS. 1Aand 1B illustrate a lighting device including a light emitting panel(LEP) in accordance with an example embodiment. The lighting device 100may be set and/or adjusted to emit an output light that has a desiredlight distribution pattern. For example, the lighting device 100 mayemit light such that a portion of an area around the lighting device 100is relatively highly illuminated by the light while another portion ofthe area is dimly illuminated.

The lighting device 100 includes the LEP 102 and a frame 104. In someexample embodiments, the lighting device 100 may also include anoptional sensor 105. The LEP 102 may be made from an acrylic material,glass, or another suitable material, that allows light to enter throughone or more narrow sides of the LEP 102 and to be emitted through one ormore broad sides of the LEP 102. The LEP 102 may have an octagonal shapeas illustrated in FIG. 1B. The LEP 102 includes a broad side 106 andeight narrow sides. The eight narrow sides may have substantially equaldimensions. Alternatively, each of the eight narrow sides may have oneor more dimensions that are different respective one or more dimensionsof some or all other narrow sides of the eight narrow sides. In someexample embodiments, the LEP 102 may include grooves on the broad side106. The LEP 102 also includes a second broad side that is opposite thebroad side 106. The second broad side may be covered with a reflectorthat reflects light toward the broad side 106. The second broad side mayalso include grooves.

The lighting device 100 includes four sets of light sources 116, 118,120, 122, which are referred to as four sets of light emitting diodes(LEDs) 116, 118, 120, 122, hereinafter. However, the four sets of lightsources 116, 118, 120, 122 may be light sources other than LEDs.Further, the terms LED and LEDs as used herein may refer to discrete LEDor LEDs, one or more organic light-emitting diodes (OLEDs), an LED chipon board that includes one or more discrete LEDs, an array of discreteLEDs, or light source(s) other than LEDs. Further, each set of lightsources 116, 118, 120, 122 may be a single light source. Continuing withFIG. 1, the four sets of LEDs 116, 118, 120, 122 are each positionedclose to a corresponding narrow side 108, 110, 112, 114 of the LEP. Toillustrate, a first set of LEDs 116 is positioned close to a firstnarrow side 108 of the LEP 102. A second set of LEDs 118 is positionedclose to a second narrow side 110 of the LEP 102. A third set of LEDs120 is positioned close to a third narrow side 112 of the LEP 102. Afourth set of LEDs 122 is positioned close to a fourth narrow side 114of the LEP 102. In some example embodiments, the sets of LEDs 116, 118,120, 122 are disposed on a respective printed circuit board (PCB).

As illustrated in FIG. 1B, the first set of LEDs 116 is positionedopposite to the third set of LEDs 120, and adjacent to the second set ofLEDs 118 and to the fourth set of LEDs 122. Similarly, the second set ofLEDs 118 is positioned opposite to the fourth set of LEDs 122, andadjacent to the first set of LEDs 116 and to the third set of LEDs 120.

In some example embodiments, the first set of LEDs 116 are configured toemit light toward the first narrow side 108 of the LEP 102. The secondset of LEDs 118 are configured to emit light toward the second narrowside 110 of the LEP 102. The third set of LEDs 120 are configured toemit light toward the third narrow side 112 of the LEP 102. The fourthset of LEDs 122 are configured to emit light toward the fourth narrowside 114 of the LEP 102.

The lighting device 100 may illuminate an area around the lightingdevice with a light emitted through the broad side 106 of the LEP 102.The lighting device 100 may emit a light through the broad side 106 ofthe LEP 102 based on one or more lights from the four sets of LEDs 116,118, 120, 122. For example, if all four sets of LEDs 116, 118, 120, 122are powered on, the light emitted by the lighting device 100 through thebroad side 106 of the LEP 102 is based on the light from each of thefour sets of LEDs 116, 118, 120, 122. As another example, if only two ofthe four sets of LEDs are powered on, the light emitted by the lightingdevice 100 through the broad side 106 of the LEP 102 is based on thelights from the two sets of LEDs that are powered. As yet anotherexample, if only one of the four sets of LEDs is powered on, the lightemitted by the lighting device 100 through the broad side 106 of the LEP102 is based only on the light from the particular set of LEDs that arepowered on.

The distribution pattern of the light emitted through the broad side 106of the LEP 102 may depend on the particular set of LEDs that are poweredon or off. For example, the distribution pattern of the light emittedthrough the broad side 106 of the LEP 102 is different when only thefirst set of LEDs 116 and the second set of LEDs 118 are powered on ascompared to when only the first set of LEDs 116 and the third set ofLEDs 120 are powered on. As another example, the distribution pattern ofthe light emitted through the broad side 106 of the LEP 102 is differentwhen only the first set of LEDs 116 and the second set of LEDs 118 arepowered on as compared to when only the second set of LEDs 118 and thefourth set of LEDs 120 are powered on.

For a fixed orientation of the lighting device 100, the distributionpattern of the light emitted through the broad side 106 of the LEP 102is different when only the first set of LEDs 116 and the second set ofLEDs 118 are powered on as compared to when only the second set of LEDs118 and the third set of LEDs 120 are powered on. Similarly, for a fixedorientation of the lighting device 100, the distribution pattern of thelight emitted through the broad side 106 of the LEP 102 is differentwhen only the first set of LEDs 116 and the third set of LEDs 120 arepowered on as compared to when only the second set of LEDs 118 and thefourth set of LEDs 122 are powered on. Thus, the distribution pattern ofthe light emitted through the broad side 106 may be changed by poweringon one or more of the sets of LEDs 116, 118, 120, 122 and powering ofthe remaining sets of LEDs 116, 118, 120, 122. By changing theparticular one or more of the sets of LEDs 116, 118, 120, 122 that arepowered on, the distribution pattern of the light emitted through thebroad side 106 can be changed.

Further, the distribution pattern of the light emitted through the broadside 106 of the LEP 102 may also depend on the intensity of light fromeach of the sets of LEDs 116, 118, 120, 122. In some exampleembodiments, the intensity of light from each powered-on set of LEDs116, 118, 120, 122 may be adjusted to various levels ranging betweenapproximately zero intensity corresponding to no light being emitted(i.e., substantially equivalent to being powered off) and the maximumintensity of light that can be emitted by the particular set of LEDs116, 118, 120, 122. In some example embodiments, intensity level oflight emitted by each one of the sets of LEDs 116, 118, 120, 122 may beset or adjusted to zero by powering off the particular set of LEDs. Theintensity of light from each one of the sets of LEDs 116, 118, 120, 122may also be preset to a desired level prior to being powered on. Thedistribution pattern of the light emitted through the broad side 106 ofthe LEP 102 may be different when one or more sets of LEDs 116, 118,120, 122 are powered to emit light at a full (i.e., one hundred percent)intensity level instead of, for example, at a substantially lessintensity level. For example, the first set of LEDs 116 and the secondset of LEDs 118 may be dimmed to emit light at fifty percent of therespective full intensity level of each set of LEDs 116, 118. Thedistribution pattern of the light emitted through the broad side 106 ofthe LEP 102 is different when the first set of LEDs 116 and the secondset of LEDs 118 are dimmed to emit light at fifty percent of theirrespective full intensity level as compared to when the first set ofLEDs 116 and the second set of LEDs 118 emit light at their respectivefull intensity level.

In some example embodiments, the full intensity level of lights emittedby the four sets of LEDs 116, 118, 120, 122 may be substantially thesame. In alternative embodiments, the full intensity level of lightemitted by some of the sets of LEDs 116, 118, 120, 122 may be differentfrom the full intensity level of light from the other sets of LEDs 116,118, 120, 122. To illustrate, the full intensity level of lights fromthe first set of LEDs 116 and from the third set of LEDs 120 may besubstantially different from the full intensity level of lights from thesecond set of LEDs 118 and from the fourth set of LEDs 122. For example,the full intensity level of light from each of the first set of LEDs 116and the third set of LEDs 120 may be approximately fifty percent of thefull intensity level of light from each of the second set of LEDs 118and the fourth set of LEDs 122. As another example, the full intensitylevel of light from each of the first set of LEDs 116 and the third setof LEDs 120 may be approximately seventy five percent of the fullintensity level of light from each of the second set of LEDs 118 and thefourth set of LEDs 122. By having different intensity levels of lightemitted by the sets of LEDs 116, 118, 120, 122, a desired distributionpattern of the light emitted through the broad side 106 of the LEP 102may be achieved.

In some example embodiments, each of the four sets of LEDs 116, 118,120, 122 may emit light that has a full intensity level that issubstantially different from the full intensity level of light emittedby all other sets of LEDs 116, 118, 120, 122. Thus, the distributionpattern of the light emitted through the broad side 106 may be changedby adjusting intensity of light emitting by one or more of the sets ofLEDs 116, 118, 120, 122.

In some example embodiments, the intensity level of light that each setof LEDs 116, 118, 120, 122 emits may be fixed. For example, the lightingdevice 100 may be designed such that some of the sets of LEDs 116, 118,120, 122 emit light approximately at a first fixed intensity level whilethe remaining sets of LEDs 116, 118, 120, 122 emit light approximatelyat a second fixed intensity level. To illustrate, one or more driversmay provide power to the sets of LEDs 116, 118, 120, 122 such that eachof the sets of LEDs 116, 118, 120, 122 emits light that has an intensitylevel intended to achieve a desired light distribution pattern.

In some example embodiments, the intensity level of light from one ormore of the set of LEDs 116, 118, 120, 122 may be set by a user, such asa consumer or a technician. To illustrate, a user may set the intensitylevel of light from each set of LEDs 116, 118, 120, 122 at time ofinstallation to achieve a desired distribution pattern of the lightemitted through the broad side of the LEP 102. For example, a user maypower on one or more of the sets of LEDs 116, 118, 120, 122 and poweroff the remaining sets of LEDs 116, 118, 120, 122 to achieve a lightdistribution pattern that reduces the level of illumination of aparticular part of the area around the lighting device 100. Further, tochange the light distribution pattern, the user may adjust the intensitylevel of the one or more sets of LEDs that are powered on. As anotherexample, a user may power on all four sets of LEDs 116, 118, 120, 122and configure each set of LEDs to emit light that has a correspondingintensity level that results in a desired distribution pattern of thelight emitted through the broad side of the LEP 102.

In some situations, several of the lighting device 100 may be installedin a particular area. For example, multiple of the lighting device 100may be installed in parking lot. In such scenarios, the lightdistribution in the parking lot may depend on distribution of light froma number of the lighting devices. Thus, overall distribution of light inthe parking lot may be controlled by adjusting the distribution of lightfrom one or more of the lighting device while considering the effect oflight emitted by the other lighting devices on the overall distributionof light.

Further, the distribution of light emitted through the broad side of theLEP 102 of the lighting device 100 may be considered in terms of theNational Electrical Manufacturers Association (NEMA) light distributionstandard and may be classified based on its NEMA type.

In some example embodiments, one or more sets of LEDs 116, 118, 120, 122may be adjustable by a user to emit light that has a desired intensitylevel. In such embodiments, alternatively or in addition to settingintensity levels at time of installation, a user may adjust theintensity level of light from each set of LEDs 116, 118, 120, 122 afterinstallation of the lighting device 100. To illustrate, afterinstallation, a user may adjust the intensity level of light from eachset of LEDs 116, 118, 120, 122 based on one or more factors, such astime of day and occupancy of the area around the lighting device 100.For example, a user may prefer that a portion of the area around thelighting device 100 is highly illuminated at all times while anotherportion of the area is highly illuminated only during a certain periodof time. To achieve light distribution pattern that matches the user'sillumination preference at different time periods, the user may, forexample, power off or dim the light from one or more of the sets of LEDs116, 118, 120, 122 as needed. Similarly, the user may power on orincrease intensity of light from the one or more of the sets of LEDs116, 118, 120, 122 as needed. In some example embodiments, a timer maybe used to control the on-off powering and/or dimming operations.

In some example embodiments, two or more of the sets of LEDs 116, 118,120, 122 may be controlled as a group. For example, the first set ofLEDs 116 and the third set of LEDs 120 may be controlled using a singlecontrol means such as a dimmer and/or a switch. Similarly, the secondset of LEDs 118 and the fourth set of LEDs 122 may be controlled using asingle control means such as a dimmer and/or a switch. Althoughparticular sets of LEDs are described as being controlled as a group, inalternative embodiments, various combinations of the sets of LEDs may becontrolled as a group. Further, as it should be apparent from the abovedescription, each of the four sets of LEDs 116, 118, 120, 122 may beindependently controlled by a corresponding dimmer and/or on-off switch(e.g., a dual in-line (DIP) switch).

In some example embodiments, a single on-off switch may be used to poweron and off all of the sets of LEDs 116, 118, 120, 122 while a dedicateddimmer is used to control a corresponding one of the sets of LEDs 116,118, 120, 122. In general, different combinations of on-off switch anddimmer control arrangements may be implemented for differentapplications.

In some example embodiments, the sensor 105 may be coupled to a switchto control whether one or more of the sets of LEDs 116, 118, 120, 122are turned on or off. For example, the sensor 105 may be a motion sensor105 that senses motion (e.g., cars, pedestrians, etc.) and provides anindication signal to an on-off switch to control whether one or more ofthe sets of LEDs 116, 118, 120, 122 are powered on or off. Alternativelyor in addition, the motion sensor 105 may also be coupled to a dimmer tocontrol the intensity level of light emitted by one or more of the setsof LEDs 116, 118, 120, 122. Although the sensor 105 is shown attached tothe LEP 102 of the lighting device 100, in alternative embodiments, thesensor 105 may be remotely located detached from the lighting device 100or may be attached to another member of the lighting device 100.

In some example embodiments, the sensor 105 may include a light sensor(in addition or alternatively to a motion sensor) that is configured todetect light and provide a corresponding indication signal to an on-offswitch to control whether one or more of the sets of LEDs 116, 118, 120,122 are powered on or off. For example, some of the sets of LEDs may bepowered on in response to the light sensor detecting low light level.Alternatively or in addition to being coupled to an on-off switch, thelight sensor may also be coupled to a dimmer to control the intensitylevel of light emitted by one or more of the sets of LEDs 116, 118, 120,122.

In some example embodiments, the frame 104 may hide the four sets ofLEDs 116, 118, 120, and 122 from view, for example, at viewing anglesbelow the lighting device 100. The frame 104 may also hide from view theoutline of the perimeter of the LEP 104. In some example embodiments,the frame 104 may be made from aluminum, and may have aesthetic feature.The frame 104 may also be part of a heat management structure of thelighting device 100. Although the frame 104 has a substantially circularshape as shown in FIG. 1A, in alternative embodiments, the frame 104 mayhave other shapes without departing from the scope of this description.

Although the LEP 102 is shown in FIG. 1B as having an octagonal shape,in some alternative embodiments, the LEP 102 may have other shapes,including a rectangular shape, a V-shape, and a circular shape, withoutdeparting from the scope of this description. In general, the LEP 102may have a polygon and other non-polygon shape and is not limited to theexample shapes identified in this description and may have fewer or morethan eight narrow sides. Each side of the LEP 102 may also be a straightor a curved side. Further, in some alternative embodiments, the lightingdevice 100 may include fewer or more than four sets of LEDs that emitlight toward correspondingly narrow sides of the LEP 102. For example,the lighting device 100 may include one, two, three, five, or more setsof LEDs that are positioned proximal to a corresponding narrow side ofthe LEP 102 having an octagonal or another shape.

To illustrate, in some example embodiments, the LEP 120 may be acircular-shape LEP. For example, multiple LEDs may be positioned aroundthe outer narrow perimeter of the circular-shape LEP, where each LED iscontrolled (i.e., powered on, power off, and/or adjusted for lightintensity) individually. Alternatively several groups of LEDs may bepositioned around the narrow outer perimeter of the circular-shape LEP,where each group of LEDs is controlled individually. By controllingindividual LEDs or groups of LEDs, distribution of light emitted by thecircular-shape LEP may be changed as desired. In an alternativeembodiment, the circular-shape LEP may have a cut-out (e.g., arectangular cut-out) through the broad sides of the circular-shape LEPand the LEDs may be positioned to emit light into the circular-shape LEPthrough the narrow side in the cut-out.

As another example, the LEP 102 may be a V-shaped LEP, and LEDs or otherlight sources that are controllable individually or in groups may bepositioned, for example, in the valley of the V-shape.

FIG. 2A illustrates the lighting device 100 of FIG. 1A including a setof LEDs that are powered on in accordance with an example embodiment.FIG. 2B illustrates an Iso-footcandle plot that corresponds to thelighting device of FIG. 2A with a single set of LEDs powered on inaccordance with an example embodiment. As illustrated in FIG. 2A, thefirst set of LEDs 116 are powered on while the other sets of LEDs 118,120, 122 shown in FIG. 1B are powered off.

Each curve of the Iso-footcandle plot shown in FIG. 2B (as well as FIGS.3B, 4B, 5B, 6B, and 7A-7D) represents locations on a viewing plane belowthe lighting device 100 that experience substantially the same lightintensity level. The center 202 of the Iso-footcandle plot represents aposition in the viewing plane that is directly below the lighting device100. Thus, points on the plot that are farthest from the center 202represent positions in the viewing plane that are farthest from thelighting device 100. Positions in the viewing plane that are representedby a particular curve experience a light intensity level that isapproximately fifty percent of the light intensity level experienced bypositions represented by an immediately adjacent inner curve.

As can be seen in FIG. 2B, when the first set of LEDs 116 are powered onand the other sets of LEDs 118, 120, 122 are powered off, some locationsin the viewing plane that are at substantially equal distances from thelighting device 100 may experience different levels of light intensity.To illustrate, some positions on the right side of the lighting device100 but that are farther away than closer positions on the left side ofthe lighting device 100 may experience relatively higher levels of lightintensity than the closer positions that are on the left side of thelighting device 100. For example, the farthest right position 204 on theouter most curve 202 experiences the same level of light intensity asthe farthest left position 206 on the curve even though the farthestright position 206 is approximately twice as far from the center 202 oflighting device 100 as the farthest left position.

Accordingly, the lighting device 100 may be set to have only the firstset of LEDs 116 powered on when a desired light distribution patterncorresponds to the pattern illustrated in FIG. 2B.

FIG. 3A illustrates the lighting device of FIG. 1A including two sets ofLEDs that are powered on in accordance with an example embodiment. FIG.3B illustrates an Iso-footcandle plot that corresponds to the lightingdevice of FIG. 3A in accordance with an example embodiment.

As illustrated in FIG. 3A, the first set of LEDs 116 and the third setof LEDs 120 are powered on and the other sets of LEDs 118, 122 arepowered off. As can be seen in FIG. 3B, some locations in the viewingplane that are at substantially equal distances from the lighting device100 may experience different levels of light intensity while otherslocations in the viewing plane that are at equal distance from thelighting device 100 may experience substantially the same level of lightintensity. Further, locations in the viewing plane that are at differentdistances from the lighting device 100 may experience substantially thesame level of light intensity. To illustrate, the farthest rightposition 304 on the outer most curve 312 and the farthest left position306 on the outer most curve 312, which are substantially at equaldistance from the lighting device 100, experience substantially the samelevel of light intensity. Similarly, the farthest back position 308 andthe farthest front position 310 on the outermost curve 312, which are atsubstantially equal distance from the lighting device 100, experiencesubstantially the same level of light intensity. However, the farthestright position 304 and the farthest left position 306 experiencesubstantially the same level of light intensity as the farthest backposition 308 and the farthest front position 310 even though thefarthest right position 304 and the farthest left position 306 aresignificantly farther away from the lighting device 100 than thefarthest back position 308 and the farthest front position 310.

Accordingly, the lighting device 100 may be set to have the first set ofLEDs 116 and the third set of LEDs 120 powered on and the other sets ofLEDs 118, 122 powered off when a desired light distribution pattern ofthe lighting device 100 corresponds to the pattern illustrated in FIG.3B.

FIG. 4A illustrates the lighting device of FIG. 1A including two sets ofLEDs that are powered on in accordance with another example embodiment.FIG. 4B illustrates an Iso-footcandle plot that corresponds to thelighting device of FIG. 4A in accordance with an example embodiment.

As illustrated in FIG. 4A, the first set of LEDs 116 and the second setof LEDs 118 are powered on and the other sets of LEDs 120, 122 arepowered off. As can be seen in FIG. 4B, some locations in the viewingplane that are at substantially equal distances from the lighting device100 may experience different levels of light intensity while otherslocations in the viewing plane that are equal distance from the lightingdevice 100 may experience substantially the same level of lightintensity. Further, locations in the viewing plane that are at differentdistances from the lighting device 100 may experience substantially thesame level of light intensity. To illustrate, the farthest rightposition 404 on the outer most curve 412 and the farthest left position406 on the outer most curve 412, which are at substantially differentdistances from the lighting device 100, experience substantially thesame level of light intensity. Similarly, the farthest back position 408and the farthest front position 410 on the outermost curve 412, whichare substantially at substantially different distances from the lightingdevice 100, experience substantially the same level of light intensity.However, the farthest right position 404 and the farthest front position410, which are at substantially equal distance from the lighting device100, experience substantially the same level of light intensity.

Accordingly, the lighting device 100 may be set to have the first set ofLEDs 116 and the second set of LEDs 118 powered on and the other sets ofLEDs 120, 122 powered off when a desired light distribution pattern ofthe lighting device 100 corresponds to the pattern illustrated in FIG.4B. Even though only two of the sets of LEDs are powered on in bothFIGS. 3A and 4A, the light distribution patterns that correspond toFIGS. 3A and 4A are significantly different from each other as can beclearly seen by comparing the corresponding Iso-footcandle plots shownin FIGS. 3B and 4B.

FIG. 5A illustrates the lighting device of FIG. 1A including three setsof LEDs that are powered on in accordance with an example embodiment.FIG. 5B illustrates an Iso-footcandle plot that corresponds to thelighting device of FIG. 5A in accordance with an example embodiment.

As illustrated in FIG. 5A, the first set of LEDs 116, the second set ofLEDs 118, and the fourth set of LEDs 120 are powered on and the thirdset of LEDs 120 are powered off. As can be seen in FIG. 5B, somelocations in the viewing plane that are at different distances from thelighting device 100 may experience substantially the same level of lightintensity. To illustrate, the farthest right position 504, the farthestback position 508 on the same curve, and the farthest front position510, which are all on the same curve 512 and significantly farther fromthe lighting device 100 than the farthest left position 506, experiencesubstantially the same level of light intensity as the farthest leftposition 506. Further, the farthest right position 504, the farthestback position 508, and the farthest front position 510, which all are atapproximately equal distances from the lighting device 100, experiencesubstantially the same level of light intensity. An overall comparisonof the Iso-footcandle plots of FIGS. 3B, 4B, and 5B shows, thedistribution pattern of the light represented by the Iso-footcandle plotof FIG. 5B is different from the light distribution patterns representedby the Iso-footcandle plots of FIGS. 3B and 4B.

Accordingly, as illustrated in FIG. 5A, the lighting device 100 may beset to have the first set of LEDs 116, the second set of LEDs 118, andthe fourth set of LEDs 120 powered on and the third set of LEDs 120powered off when a desired light distribution pattern of the lightingdevice 100 corresponds to the pattern illustrated in FIG. 5B.

FIG. 6A illustrates the lighting device of FIG. 1A including four setsof LEDs that are powered on in accordance with an example embodiment.FIG. 6B illustrates an Iso-footcandle plot that corresponds to thelighting device of FIG. 6A in accordance with an example embodiment. Asillustrated in FIG. 6A, all four sets of LEDs 116, 118, 120, 122 arepowered on. As can be seen in FIG. 6B, unlike the light distributionpattern illustrated in FIGS. 3B, 4B, and 5B, all locations in theviewing plane that are substantially equally distanced from the lightingdevice 100 experience substantially the same level of light intensity.In addition, the overall distribution pattern of the light representedby the Iso-footcandle plot of FIG. 6B is different from the lightdistribution patterns represented by the Iso-footcandle plots of FIGS.3B, 4B, and 5B.

FIGS. 7A-7D are Iso-footcandle plots illustrating effects of differentintensity levels of lights from different light sources on the lightdistribution pattern of a lighting device in accordance with an exampleembodiment. For illustrative purposes, the inner curve in each of theIso-footcandle plots of FIGS. 7A-7D may be a 0.2 foot-candle (fc) curve,and the outer curve may be a 0.1 fc curve.

In an example embodiment, the Iso-footcandle plot on FIG. 7A correspondsto the lighting device 100 illustrated in FIG. 6A, where all four setsof LEDs 116, 118, 120, 122 are powered on. For example, theIso-footcandle plot on FIG. 7A may correspond to all four sets of LEDs116, 118, 120, 122 emitting light that are each substantially at a fullintensity level. In some example embodiments, the Iso-footcandle plot onFIG. 7B may correspond to the lighting device 100 illustrated in FIG.6A, where the first set of LEDs 116 and the third set of LEDs 120 emitlight at substantially full intensity level, and where the second set ofLEDs 118 and the fourth set of LEDs 122 emit light at substantiallyfifty percent of the full intensity level. In some example embodiments,the Iso-footcandle plot on FIG. 7C may correspond to the lighting device100 illustrated in FIG. 6A, where the first set of LEDs 116 and thethird set of LEDs 120 emit light at substantially full intensity level,and where the second set of LEDs 118 and the fourth set of LEDs 122 emitlight at substantially twenty five percent of the full intensity level.In some example embodiments, the Iso-footcandle plot on FIG. 7D maycorrespond to the lighting device 100 illustrated in FIG. 3A, where thefirst set of LEDs 116 and the third set of LEDs 120 emit light at asubstantially full intensity level, and where the second set of LEDs 118and the fourth set of LEDs 122 are powered off (alternatively, dimmed tosubstantially zero percent of the full intensity level).

As comparison of the Iso-footcandle plots of FIGS. 7A-7D illustrates,changes in the intensity level of light emitted by two of the sets ofLEDs 116, 118, 120, 122 affects the light distribution pattern of thelighting device 100. Accordingly, the lighting device 100 may beconfigured to emit light that has a particular light distributionpattern by setting or adjusting one or more of the sets of LEDs 116,118, 120, 122 to emit a light that has a particular level of intensity.

Although FIGS. 7A-7D are described with respect to four sets of LEDswhere intensity level of light from two of the four sets of LEDs are setor adjusted, in alternative embodiments, only one or more than two ofthe four sets may be set and/or adjusted to emit light so that each haveparticular levels of intensity to produce a particular distributionpattern of the light from the lighting device 100. Further, as describedabove, in some alternative embodiments, the lighting device 100 may havefewer or more than four sets of LEDs. In addition, although particularlevels of light intensity are described, the intensity of light fromeach set of LEDs may be adjusted to have a level ranging between a fullintensity level and substantially being powered off. Further, asdescribed above, in some example embodiments, the level of lightintensity of light from each set of LEDs may be independentlycontrolled.

FIG. 8 is a flowchart illustrating a method of controlling lightdistribution pattern of an edge-lit lighting device in accordance withan example embodiment. The method 800 includes installing an edge-litlighting device, at step 802. For example, a technician may install theedge-lit lighting device, such as the edge-lit lighting device 100 ofFIG. 1A. To illustrate, the edge-lit lighting device may include a lightemitting panel (LEP), a first plurality of light emitting diodes (LEDs)positioned proximal to a first narrow side of the LEP and configured toemit a first light toward the first narrow side, and a second pluralityof LEDs positioned proximal to a second narrow side of the LEP andconfigured to emit a second light toward the second narrow side. Forexample, the first plurality of LEDs may correspond to the first set ofLEDs 116 of FIG. 1B. Similarly, the second plurality of LEDs maycorrespond to, for example, the second set of LEDs 118 or the third setof LEDs 120 of FIG. 1B.

The method 800 further includes setting an intensity level of the firstlight, at step 804. For example, the first plurality of LEDs may be setto emit light at a full intensity level. The method 800 also includessetting an intensity level of the second light, at step 806. Forexample, the second plurality of LEDs may be set to emit light at a fullintensity level as well. Alternatively, the second plurality of LEDs maybe set to emit light at approximately fifty percent of the fullintensity level.

In some example embodiments, the method 800 also includes adjusting theintensity level of the first light, at step 808. For example, adjustingthe intensity level of the first light may include dimming the firstlight. Alternatively or in addition, the method 800 may also includeadjusting the intensity level of the second light.

Although particular embodiments have been described herein in detail,the descriptions are by way of example. The features of the embodimentsdescribed herein are representative and, in alternative embodiments,certain features, elements, and/or steps may be added or omitted.Additionally, modifications to aspects of the embodiments describedherein may be made by those skilled in the art without departing fromthe spirit and scope of the following claims, the scope of which are tobe accorded the broadest interpretation so as to encompass modificationsand equivalent structures.

What is claimed is:
 1. An edge-lit lighting fixture, comprising: a lightemitting panel (LEP); a first light emitting diode (LED) light sourcepositioned proximal to a narrow outer perimeter edge of the LEP andconfigured to emit a first light into the LEP through the narrow outerperimeter edge, the first light having a first intensity level; a secondLED light source positioned proximal to the narrow outer perimeter edgeof the LEP and configured to emit a second light into the LEP throughthe narrow outer perimeter edge, the second light having a secondintensity level, wherein the first LED light source and the second LEDlight source are positioned at different locations proximal to thenarrow outer perimeter edge of the LEP; and a motion sensor positionedat a broad surface of the LEP to detect a motion in an area, wherein thefirst LED light source and the second LED light source are powered onbased on the motion sensor, and wherein the edge-lit lighting fixture isconfigured to provide an illumination light that illuminates the areathrough the broad surface of the LEP, the illumination light resultingfrom the first light and the second light that are emitted into the LEPthrough the narrow outer perimeter edge of the LEP.
 2. The edge-litlighting fixture of claim 1, wherein the LEP has a circular shape. 3.The edge-lit lighting fixture of claim 2, wherein the motion sensor ispositioned at a center of the broad surface of the LEP.
 4. The edge-litlighting fixture of claim 1, wherein the first LED light source and thesecond LED light source are positioned opposite to each other withrespect to the LEP.
 5. The edge-lit lighting fixture of claim 1, whereinthe first LED light source and the second LED light source arepositioned approximately 90 degrees from each other with respect to acenter of the LEP.
 6. The edge-lit lighting fixture of claim 1, furthercomprising a frame positioned adjacent the narrow outer perimeter edgeof the LEP.
 7. The edge-lit lighting fixture of claim 6, wherein theframe has a circular outer perimeter and a circular inner perimeter,wherein the first LED light source and the second LED light source arecovered from view by the frame from below the edge-lit lighting fixture.8. The edge-lit lighting fixture of claim 1, wherein the first intensitylevel and the second intensity level are different from each other. 9.The edge-lit lighting fixture of claim 1, wherein the first intensitylevel and the second intensity level are adjustable to intensity levelsthat are different from each other, and wherein a distribution patternof the illumination light is changeable by adjusting one of the firstintensity level and the second intensity level.
 10. The edge-litlighting fixture of claim 1, wherein the LEP has a polygon shape.
 11. Anedge-lit lighting fixture, comprising: a light emitting panel (LEP); afirst light emitting diode (LED) light source positioned proximal to anarrow outer perimeter edge of the LEP and configured to emit a firstlight into the LEP through the narrow outer perimeter edge; a second LEDlight source positioned proximal to the narrow outer perimeter edge ofthe LEP and configured to emit a second light into the LEP through thenarrow outer perimeter edge, wherein the first LED light source and thesecond LED light source are positioned at different locations proximalto the narrow outer perimeter edge of the LEP; and a motion sensorpositioned at a broad surface of the LEP to detect a motion in an area,wherein the first LED light source and the second LED light source arepowered on based on the motion sensor and wherein the edge-lit lightingfixture provides an illumination light that illuminates the area throughthe broad surface of the LEP, the illumination light resulting from thefirst light and the second light that are emitted into the LEP throughthe narrow outer perimeter edge of the LEP.
 12. The edge-lit lightingfixture of claim 11, further comprising a frame positioned adjacent thenarrow outer perimeter edge of the LEP.
 13. The edge-lit lightingfixture of claim 12, wherein the motion sensor and at least a portion ofthe broad surface of the LEP are viewable from below the edge-litlighting fixture.
 14. The edge-lit lighting fixture of claim 13, whereinthe first LED light source and the second LED light source are hiddenfrom view by the frame from below the edge-lit lighting fixture.
 15. Theedge-lit lighting fixture of claim 11, wherein the LEP has a circularshape.
 16. The edge-lit lighting fixture of claim 11, wherein the LEPhas a polygon shape.
 17. An edge-lit lighting fixture, comprising: alight emitting panel (LEP) having a broad surface and a narrow outerperimeter edge around the broad surface; light emitting diode (LED)light sources, wherein each LED light source of the LED light sources ispositioned at a respective location proximal to the narrow outerperimeter edge of the LEP and oriented to emit a respective light intothe LEP through the narrow outer perimeter edge of the LEP; a framehaving a circular inner perimeter and a circular outer perimeter,wherein the frame is positioned adjacent the narrow outer perimeter ofthe LEP; and a motion sensor positioned at the broad surface of the LEPto detect a motion in an area, wherein a first LED light source and asecond LED light source are powered on based on the motion sensor, andwherein the edge-lit lighting fixture provides an illumination lightthat illuminates the area, the illumination light resulting from therespective lights emitted into the LEP through the narrow outerperimeter edge of the LEP.
 18. The edge-lit lighting fixture of claim17, wherein the broad surface of the LEP is exposed for view from belowthe edge-lit lighting fixture.
 19. The edge-lit lighting fixture ofclaim 18, wherein the LED light sources are hidden from view by theframe from below the edge-lit lighting fixture.
 20. The edge-litlighting fixture of claim 18, wherein the LEP has a circular shape or apolygon shape.